To detect steam flow rates, current systems utilize vortex shedding meters, orifice plate flow meters, turbine flow meters, Coriolis mass flow meters, resistance thermometer flow meters, and ultrasonic flow meters, all of which have resulted in a variety of different costs and deficiencies. Some of the problems these flow meters have created include the impedance of the steam flow, the high maintenance costs from moving parts, and low accuracy. Most of these systems require the presence of a physical object in the path of the steam that results in low turndown ratios (the range of flow a flow meter can measure). Additionally, these systems are often susceptible to saturated steam that can condense onto an obtrusion and result in inaccurate mass flow readings. Other problems include their inability to detect sudden fluctuations present in the steam flow rate generated by pressure or temperature variations within these systems.
Laser-based systems generally measure the quality of steam (liquid phase of water as opposed to the vapor phase). Those laser-based systems that attempt to measure mass flow rely on phase change measurements or other more complex methods.